The problem of gas bubble detection in a liquid occurs in many processes from fermentation to cavitation. Bubble detection in a liquid is especially necessary in resonant chemical reactions or chemical reactions that are not self limiting. An example of a resonant chemical reaction is the reaction of highly concentrated hydrogen peroxide with organic material as temperature is increased or held constant at an elevated temperature. The hydrogen peroxide reacts with the organic material at a resonant or ever increasing rate. To avoid over pressure, overflow or other operational problems, the bubble formation must be monitored and the hydrogen peroxide/organic mixture removed from the elevated temperature environment upon observing excessive bubble formation.
More specifically, the Environmental Protection Agency (EPA) soil testing procedure EPA Method #3050 from SW-846 involves multiple acid digestion steps followed by an organic removal step utilizing highly concentrated hydrogen peroxide. In practice, multiple flasks each having a soil sample are subjected to the acid digestion and organic removal. The organic removal involves the use of concentrated (about 30 mol %) hydrogen peroxide that is heated. One of the major requirements of the EPA procedures is to avoid runaway of oxygen effervescence during organic removal. Upon observation of a run away condition, the operator immediately removes the heat source either by switching it off or by removing the flask from the heat source until the run away condition is overcome. Personnel monitoring many flasks are constantly removing run-away flasks and replacing calmed flasks in order to satisfy the EPA Methods and provide reliable soil sample preparation. Clearly, this is labor intensive and subject to human error, especially upon fatigue of the monitoring personnel.